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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>合并两个有序链表</title>
  </head>
  <body>
    <script>
      // 将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。

      // 示例一
      // 输入：l1 = [1,2,4], l2 = [1,3,4]
      // 输出：[1,1,2,3,4,4]

      // --------------------------------
      var mergeTwoLists = function (l1, l2) {
        if (l1 === null) {
          return l2;
        }
        if (l2 === null) {
          return l1;
        }
        if (l1.val < l2.val) {
          l1.next = mergeTwoLists(l1.next, l2);
          return l1;
        } else {
          l2.next = mergeTwoLists(l1, l2.next);
          return l2;
        }
      };
    </script>
  </body>
</html>
